1. Field of the Invention
The present invention relates to an electromagnetic device, especially to a release type electromagnetic device including a permanent magnet for attracting a movable iron armature and exciting coils for providing a magnetic flux opposing the flux of the permanent magnet, in order to release the iron armature.
2. Description of the Prior Art
As a release type electromagnetic device in the prior art, a device as shown in FIG. 1 has been proposed. In this device, a movable iron armature 1 is attracted by the magnetic flux .phi..sub.1 generated by a permanent magnet 4, and a magnetic flux .phi..sub.2 is generated by supplying current to exciting coils 5, 6, for releasing movable iron armature 1 by the magnetic flux .phi..sub.2. However, in the case of such device, since the magnetic flux .phi..sub.2 generated by the coils 5, 6 forms a closed magnetic circuit through the permanent magnet 4, which has very large magnetic reluctance, it is reduced in strength. Thus the current to be supplied to the coils 5, 6, for releasing the magnetic pole faces 1a, 1a' of the movable iron armature 1 from the magnetic pole faces 2a, 2a' of the yokes 2, 2' has to be very large in magnitude in the case of such conventional device.